1. Field of the Invention
The present invention relates to a side airbag apparatus for protecting a passenger, at the time of a transverse collision of a vehicle, against a secondary collision and, more particularly, to a side collision sensor system for inflating an airbag by detecting the side collision.
2. Description of the Prior Art
An airbag to be expanded for protecting a passenger at the time of a transverse collision or the like of a vehicle is inflated with gas which is generated by an inflater forming part of the airbag apparatus, for example. Especially, an electric airbag apparatus is equipped with electric sensors including pressure sensitive sensors and/or contact sensors. These sensors output signals if they detect a collision. In response to the signals, a gas generating agent in the inflater is ignited to generate a mass of gas instantly. This gas fills up and inflates the airbag abruptly so that the airbag is expanded between the passenger and the inner side wall such as the side door inner face of a vehicle compartment to protect the passenger against a secondary collision.
For example, FIG. 9 shows one example of the side airbag apparatus of the prior art, as disclosed in U.S. Pat. No. 4,966,388. This apparatus has a side airbag 101 confined in a folded state inside of the side door or the like at the side face of a vehicle. At the time of a side collision, an inflater 102 is ignited to generate gas, which inflates the side airbag 101 so that the side airbag 101 is expanded in the space between the a driver D and the inner face of a side door 103.
The side airbag 101 of the prior art is fixed together with the inflater 102 on a backup plate 104, which in turn is mounted on an inner panel or the like in the side door 103 and has its compartment inner side covered removably with a trim cover 105. In the side airbag apparatus thus constructed, therefore, a side collision sensor 106 elongated fully to the door width in the side door 103 ignites the inflater 102 if it is partially compressed and turned ON at the time of a side collision. Then, the side airbag 101 is inflated with the gas generated from the inflater 102 and is expanded to a predetermined position, while opening the trim cover 105 forcibly into the compartment, to protect a driver against a secondary collision.
In short, in this side airbag apparatus, the side airbag 101 is attached to a predetermined position in each side door 103. In the same side door 103, there is also mounted the side collision sensor 106 for detecting a side collision by having its contacts connected when compressed. If this vehicle body has its side door 103 hit by another vehicle, the side collision sensor 106 in the side door 103 is turned ON so that the side airbag 101 is inflated in response to the signal of the side collision sensor 106 to protect the passenger.
In the side airbag apparatus of the prior art thus far described, however, the side collision sensor 106 in the side door 103 cannot detect a side collision, if this side collision takes place in a portion of the side face of the vehicle body other than the side door 103, namely, in the side portion of a front fender or a rear fender, which is not equipped with the side collision sensor 106. In case of this collision, therefore, the side airbag 101 is left uninflated. Since, however, the vehicle body receives a high transverse load even in case of the side collision at the front or rear fender, the driver D is also pushed sideways on his seat by the inertial load of the side collision of this kind. In this case, too, the driver has to be protected against the secondary collision by inflating the airbag 101. If the vehicle body has its side hit near the front or rear end so that it is turned or spun, the position of the airbag to be expanded is different because the direction of the inertial load to be exerted upon the driver is different depending upon the position of its spinning center and the position of the driver.